Papillary muscle traction in mitral valve prolapse: quantitation by two-dimensional echocardiography

CMR predictors of mitral regurgitation in mitral valve prolapse

OBJECTIVES

We sought to assess the correlation between mitral valve characteristics and severity of mitral regurgitation (MR) in subjects with mitral valve prolapse (MVP) undergoing cardiac magnetic resonance (CMR) imaging.

BACKGROUND

Compared with extensive echocardiographic studies, CMR predictors of MVP-related MR are unknown. The severity of MR at the time of diagnosis has prognostic implication for patients; therefore, the identification of determinants of MR and its progression may be important for risk stratification, follow-up recommendations, and surgical decision making.

METHODS

Seventy-one MVP patients (age 54 ± 11 years, 58% males, left ventricular [LV] ejection fraction 65 ± 5%) underwent cine CMR to assess annular dimensions, maximum systolic anterior and posterior leaflet displacement, papillary muscle (PM) distance to coaptation point and prolapsed leaflets, as well as diastolic anterior and posterior leaflet thickness and length, and LV volumes and mass. Velocity-encoded CMR was used to obtain aortic outflow and to quantify MR volume.

RESULTS

Using multiple linear regression analysis including all variables, LV mass (p < 0.001), anterior leaflet length (p = 0.006), and posterior displacement (p = 0.01) were the best determinants of MR volume with a model-adjusted R(2) = 0.6. When the analysis was restricted to valvular characteristics, MR volume correlated with anterior mitral leaflet length (p < 0.001), posterior mitral leaflet displacement (p = 0.003), posterior leaflet thickness (p = 0.008), and the presence of flail (p = 0.005) with a model-adjusted R(2) = 0.5. We also demonstrated acceptable intraobserver and interobserver variability in these measurements.

CONCLUSIONS

Anterior leaflet length, posterior leaflet displacement, posterior leaflet thickness, and the presence of flail are the best CMR valvular determinants of MVP-related MR. The acceptable intraobserver and interobserver variability of our measurements confirms the role of CMR as an imaging modality for assessment of MVP patients with significant MR.

Evaluation of papillary muscle function using cardiovascular magnetic resonance imaging in mitral valve prolapse

Abnormal traction and excursion of the papillary muscle (PM) can be observed in patients with mitral valve prolapse (MVP) and can adversely affect the electrophysiologic stability of the underlying myocardium. Cardiovascular magnetic resonance (CMR) techniques can directly measure the excursion and velocity of PM tips during ventricular systole. In addition, high-resolution late gadolinium enhancement (LGE) CMR imaging allows for visualization of the underlying potentially arrhythmogenic PM fibrosis substrate. We prospectively studied 16 patients with MVP and 9 healthy adult subjects using phase-contrast CMR and cine CMR to assess the PM velocity and excursion. LGE CMR was performed in 13 patients with MVP (81%). The peak PM systolic velocity and maximum PM excursion were significantly increased in those with MVP (12 +/- 5 vs 5 +/- 2 cm/s and 15 +/- 5 vs 2 +/- 3 mm, both p <0.001). Definite PM LGE was found in 6 patients (46%) but the finding did not correlate with PM velocity or excursion. In conclusion, functional CMR imaging demonstrated increased peak PM systolic velocity and excursion distance in patients with MVP. These parameters, however, did not relate to underlying PM fibrosis.

QT dispersion and diastolic functions in differential diagnosis of primary mitral valve prolapse and rheumatic mitral valve prolapse

There is no specific criteria established to guide physicians in the differential diagnosis of primary mitral valve prolapse (MVP) and rheumatic MVP. Previous studies suggested that history and pathology of mitral valve could be helpful in differential diagnosis of MVP. The aim of this study was to evaluate the value of QT interval, QT dispersion, and diastolic function in differential diagnosis of MVP. We examined electrocardiographies and echocardiographies of 24 primary MVP patients, 20 rheumatic MVP patients, and 21 healthy subjects. MVP was defined as superior displacement of the mitral leaflets more than 2 mm into the left atrium during systole. QT dispersion was significantly higher in primary MVP patients (71 +/- 13.5 ms, p < 0.01). Maximum QT dispersion value in rheumatic MVP patients was 55 ms. E and A velocity values which show ventricular early and late diastolic filling, were lower in primary MVP patients (p < 0.01). There was no difference in the heart rate corrected QT interval values between the primary MVP patients (397 +/- 28.1), rheumatic MVP patients (403 +/- 23.8) and healthy children (404 +/- 15.8; p > 0.05). Our findings may indicate that QT dispersion can be used as a parameter for differential diagnosis of primary MVP and rheumatic MVP. Further studies are needed to identify a cut-off point of QT dispersion.

Study of the traction resistance of mitral valve chordae tendineae

OBJECTIVE

To determinate the extension and the resistance of the primary mitral valve chordae tendineae when submitted to traction. The importance of keeping the integrity of papillary muscle, chordae tendineae, and mitral valve cuspid when the replacement of this valve occurs is clear, but the knowledge of the maximum resistance that a primary tendinea chorda can withstand is not known.

METHODS

Eight hearts were dissected, and one hundred and thirty two primary human chordae tendineae were measured (length and thickness) and submitted to traction under controlled conditions so that the absolute resistance, resistance relative to thickness (relative resistance), and elongation could be measured.

RESULTS

The correlation between the elongation at the moment of rupture and the thickness was equal to 1.54 + 17.02 x thickness (P = 0.026); and to absolute resistance was equal to 0.95 + 1.42 x resistance (P < 0.001); and to the resistance relative to thickness (relative resistance) was equal to 1.95 + 0.08 x relative resistance (P = 0.009). The correlation between the absolute resistance and the thickness was equal to 0.26 + 14.53 x thickness (P < 0.001).

CONCLUSION

The resistance of primary mitral valve chordae tendineae is associated with its thickness and elongation at the moment of rupture, but is not associated with the length. The elongation at the moment of rupture shows a relationship with the resistance relative to thickness (relative resistance) and with the thickness of the primary chordae tendineae, but not with the length of the chordae tendineae.

Fluid Mechanics of Heart Valves

Valvular heart disease is a life-threatening disease that afflicts millions of people worldwide and leads to approximately 250,000 valve repairs and/or replacements each year. Malfunction of a native valve impairs its efficient fluid mechanic/hemodynamic performance. Artificial heart valves have been used since 1960 to replace diseased native valves and have saved millions of lives. Unfortunately, despite four decades of use, these devices are less than ideal and lead to many complications. Many of these complications/problems are directly related to the fluid mechanics associated with the various mechanical and bioprosthetic valve designs. This review focuses on the state-of-the-art experimental and computational fluid mechanics of native and prosthetic heart valves in current clinical use. The fluid dynamic performance characteristics of caged-ball, tilting-disc, bileaflet mechanical valves and porcine and pericardial stented and nonstented bioprostheic valves are reviewed. Other issues related to heart valve performance, such as biomaterials, solid mechanics, tissue mechanics, and durability, are not addressed in this review.

Mitral valve prolapse in the general population: the benign nature of echocardiographic features in the Framingham Heart Study

OBJECTIVE

The aim of this study was to examine the echocardiographic features and associations of mitral valve prolapse (MVP) diagnosed by current two-dimensional echocardiographic criteria in an unselected outpatient sample.

BACKGROUND

Previous studies of patients with MVP have emphasized the frequent occurrence of echocardiographic abnormalities such as significant mitral regurgitation (MR) and left atrial (LA) enlargement that are associated with clinical complications. These studies, however, have been limited by the use of hospital-based or referral series.

METHODS

We quantitatively studied all 150 subjects with possible MVP by echocardiography and 150 age- and gender-matched subjects without MVP from the 3,491 subjects in the Framingham Heart Study. Based on leaflet morphology, subjects were classified as having classic (n = 46), nonclassic (n = 37), or no MVP.

RESULTS

Leaflet length, MR degree, and LA and left ventricular size were significantly but mildly increased in MVP (p < 0.0001 to 0.004), with mean values typically within normal range. Average MR jet area was 15.1 +/- 1.4% (mild) in classic MVP and 8.9 +/- 1.5% (trace) in nonclassic MVP; MR was severe in only 3 of 46 (6.5%) subjects with classic MVP, and LA volume was increased in only 8.7% of those with classic MVP and 2.7% of those with nonclassic MVP.

CONCLUSIONS

Although the echocardiographic characteristics of subjects with MVP in the Framingham Heart Study differ from those without MVP, they display a far more benign profile of associated valvular, atrial, and ventricular abnormalities than previously reported in hospital- or referral-based series. Therefore, these findings may influence the perception of and approach to the outpatient with MVP.

Is mitral valve prolapse due to cardiac entrapment in the chest Cavity? A CT view

BACKGROUND

Mitral valve prolapse (MVP) is the most frequently diagnosed valvular disease, but its pathophysiology remains elusive. Its complete absence in 1,734 neonatal echocardiographic studies suggests that this may be an acquired rather than a congenital disease. We observed several patients with distorted cardiac and valvular anatomies on electron beam CT (EBCT) images of the chest who reported symptoms reminiscent of MVP. In these patients, the heart is compressed between the spine and the anterior chest wall and it appears trapped in a chest cavity that is too small for its size.

METHODS

We performed EBCT in 66 patients with echocardiographically proven MVP and no clinical pectus excavatum (group A; 80% were women; mean age, 48 +/- 12 years) and in 96 control patients without MVP by echocardiography (group B; 72% were women; mean age, 49 +/- 10 years). EBCT alone was also performed on 200 patients who had reported atypical chest discomfort and palpitations to their physicians (group C) and on 200 asymptomatic patients (group D). The EBCT measurements included the following: anteroposterior chest diameter (APD); the angle formed by the confluence of the mitral valve ring with the interatrial septum (ANGLE); and the contact area between the posterior surface of the anterior chest wall and the myocardium (CA). Entrapment was considered present if the individual patient's measurements varied by more than two SDs compared to measurements made in control subjects (group B).

RESULTS

EBCT images demonstrated cardiac entrapment in 82% of group A patients and in 4.2% of group B patients (p < 0.001). ANGLE and CA were significantly larger in MVP patients than in group B patients (114 +/- 9 degrees vs 91 +/- 5 degrees and 6,230 +/- 2,020 mm(2) vs 476 +/- 1,009 mm(2), respectively; p < 0.001 for both comparisons), while APD was significantly smaller (91 +/- 16 mm vs 128 +/- 17 mm, respectively; p < 0.001). The prevalence of entrapment was significantly greater in group C patients than in group D patients (22% vs 6.5%; p < 0. 001).

CONCLUSIONS

MVP may be an acquired condition caused by a growth disproportion between the heart and the chest cavity, with distortion of the mitral valve annulus and subsequent leaflet prolapse. A narrow APD, a wide ANGLE, and a large CA characterize this condition. Similar findings are found in a sizable proportion of patients with atypical chest pain symptoms and palpitations.

Mechanism of dynamic regurgitant orifice area variation in functional mitral regurgitation: physiologic insights from the proximal flow convergence technique

OBJECTIVES

We used the Doppler proximal flow convergence technique as a physiologic tool to explore the effects of the time courses of mitral annular area and transmitral pressure on dynamic changes in regurgitant orifice area.

BACKGROUND

In functional mitral regurgitation (MR), regurgitant flow rate and orifice area display a unique pattern, with peaks in early and late systole and a midsystolic decrease. Phasic changes in both mitral annular area and the transmitral pressure acting to close the leaflets, which equals left ventricular-left atrial pressure, have been proposed to explain this dynamic pattern.

METHODS

In 30 patients with functional MR, regurgitant orifice area was obtained as flow (from M-mode proximal flow convergence traces) divided by orifice velocity (v) from the continuous wave Doppler trace of MR, transmitral pressure as 4v(2), and mitral annular area from two apical diameters.

RESULTS

All patients had midsystolic decreases in regurgitant orifice area that mirrored increases in transmitral pressure, while mitral annular area changed more gradually. By stepwise multiple regression analysis, both mitral annular area and transmitral pressure significantly affected regurgitant orifice area; however, transmitral pressure made a stronger contribution (r2 = 0.441) than mitral annular area (added r2 = 0.008). Similarly, the rate of change of regurgitant orifice area more strongly related to that of transmitral pressure (r2 = 0.638) than to that of mitral annular area (added r2 = 0.003). A similar regurgitant orifice area time course was observed in four patients with fixed mitral annuli due to Carpentier ring insertion.

CONCLUSIONS

In summary, the time course and rate of change of regurgitant orifice area in patients with functional MR are predominantly determined by dynamic changes in the transmitral pressure acting to close the valve. Thus, although mitral annular area helps determine the potential for MR, transmitral pressure appears important in driving the leaflets toward closure, and would be of value to consider in interventions aimed at reducing the severity of MR.

Evaluation of mitral valve disease using transesophageal echocardiography

In the past 10 years, clinical application of transesophageal echocardiography (TE) has grown explosively. Intraoperative TE offers a powerful diagnostic and monitoring tool for the physicians in the cardiac operating room. The use of TE revolutionizes the assessment of patients with mitral valve disease. Surgical decisions are often altered based on the information obtained from TE. This review describes the basic features of TE as well as its uses in the intraoperative setting for evaluation of the mitral valve.

A three-component force vector cell for in vitro quantification of the force exerted by the papillary muscle on the left ventricular wall

Recent clinical studies indicate that functional mitral regurgitation, which is a common complication in patients who suffer from ischemic heart disease, is related to an increase in the tethering forces acting on the mitral valve leaflets. Alterations in the valvular assembly, displacement of the papillary muscles or dilatation of the mitral valve annulus can disrupt the normal force balance on the mitral leaflets and result in an abnormal coaptation geometry with incomplete mitral leaflet closure. The force balance imposed on the mitral leaflets is created by the coapting forces generated by the transmitral pressure difference and the tethering forces at the leaflet attachments. A unique force vector cell capable of accurately measuring the three-component force vector applied by the papillary muscle on the left-ventricular wall was designed and manufactured to permit quantification of the alteration in the force balance acting on the mitral leaflets, and to allow for the study of the influence of papillary muscle displacement on mitral regurgitation.

Is mitral valve prolapse a congenital or acquired disease?

The prevalence of mitral valve prolapse (MVP) at birth was studied in 1,734 consecutive newborns without congenital structural heart disease. We have not identified any case of an unequivocal pattern of MVP using auscultatory and echocardiographic diagnostic criteria. Our data argue for the concept that MVP is an acquired disease.

Excessive papillary muscle traction and dilated mitral annulus in mitral valve prolapse without mitral regurgitation

This study demonstrated excessive papillary muscle displacement during peak systole but normal mitral annulus function during the cardiac cycle in patients with mitral valve prolapse and no mitral regurgitation. The excessive papillary muscle displacement may play an important role in the pathogenesis of the superior displacement of mitral leaflets in patients with mitral valve prolapse.

Transesophageal echocardiographic assessment of the contribution of intrinsic tissue thickness to the appearance of a thick mitral valve in patients with mitral valve prolapse

OBJECTIVES

This prospective, blinded transesophageal echocardiographic study was performed to determine the relative contributions of leaflet redundancy and overlap versus intrinsic tissue thickening as mechanisms for the apparent increase in diastolic thickness of the mitral valve.

BACKGROUND

Increased diastolic thickness of the mitral valve has been identified as an echocardiographic feature that predicts subsequent adverse sequelae in patients with mitral valve prolapse (MVP).

METHODS

Eleven patients with clinical and transthoracic echocardiographic evidence of MVP and 11 age-matched control subjects underwent protocol transesophageal echocardiography to image the mitral valve in two orthogonal planes and to measure its thickness in systole and diastole.

RESULTS

Maximal diastolic width of the slack, unloaded anterior leaflet was significantly greater in patients with MVP than in control subjects (mean +/- SD: 0.64 +/- 0.20 cm vs. 0.30 +/- 0.04 cm, p < 0.001). Similarly, diastolic posterior leaflet width was greater in patients with MVP (0.67 +/- 0.39 cm vs. 0.31 +/- 0.06 cm, p < 0.01). In contrast, minimal systolic width of the distended pressure-loaded mitral valve was not significantly different between patients with MVP and control subjects for either the anterior (0.22 +/- 0.05 cm vs. 0.20 +/- 0.04 cm, p = NS) or the posterior (0.25 +/- 0.07 cm vs. 0.24 +/- 0.05 cm, p = NS) leaflets. The percent change in leaflet width from diastole to systole (% delta W), an index of the contribution of dynamic factors (e.g., leaflet redundancy and overlap) to the apparent increase in diastolic leaflet thickness, was significantly greater in patients with MVP than in control subjects for both the anterior (% delta W 62 +/- 13% vs. 34 +/- 16%, p < 0.001) and the posterior (% delta W 54 +/- 19% vs. 22 +/- 21%, p < 0.005) leaflets.

CONCLUSIONS

The apparent increase in diastolic mitral leaflet thickness in patients with MVP versus control subjects is largely attributable to dynamic factors such as leaflet redundancy, overlap and deformation. During diastole, when the mitral leaflets are slack and unstressed, the leaflets appear markedly thickened in patients with MVP. In contrast, during systole, when developed intraventricular pressure distends the leaflets, causing them to stretch and balloon into the left atrium, the intrinsic tissue thickness is much less than that measured in diastole. These findings have important implications for the morphologic criteria used to diagnose MVP and the potential pathophysiologic mechanisms for adverse sequelae in this syndrome.

Changes in effective regurgitant orifice throughout systole in patients with mitral valve prolapse. A clinical study using the proximal isovelocity surface area method

BACKGROUND

In patients with mitral valve prolapse, spontaneous changes of the effective regurgitant orifice during systole are not well documented. Such changes can now be analyzed by use of the proximal isovelocity surface area method, but the changes raise concern about the reliability of this method for assessing overall severity of regurgitation in these patients.

METHODS AND RESULTS

In a prospective study of 42 patients with mitral valve prolapse, the effective mitral regurgitant orifice was calculated at four phases of systole (early, mid, mid-late, and late) as the ratio of regurgitant flow to regurgitant velocity by use of the proximal isovelocity surface area method. Throughout systole, the effective regurgitant orifice increased significantly, from 32 +/- 27 mm2 in early systole to 41 +/- 27 in midsystole, 55 +/- 30 in mid-late systole, and 107 +/- 66 mm2 during late systole (P < .0001). Phasic regurgitant volume increased from early to mid-late systole but decreased in late systole. For quantitation of the overall effective regurgitant orifice, four approaches using the proximal isovelocity surface area were compared with simultaneously performed quantitative Doppler echocardiography (54 +/- 30 mm2) and quantitative two-dimensional echocardiography (51 +/- 29 mm2). All correlations were good (r > .95), but overestimation was considerable when the largest flow convergence was used (70 +/- 39 mm2; both P < .0001), significant when the simple mean of the four phases was used (59 +/- 36 mm2; P = .005 and P = .0007, respectively), mild when a weighted mean of the four phases was used (55 +/- 33 mm2; P = .41 and P = .01, respectively), and no overestimation was observed when the effective regurgitant orifice calculated at maximum regurgitant velocity was used (54 +/- 30 mm2; P = .29 and P = .17, respectively).

CONCLUSIONS

Phasic changes of mitral regurgitation are observed in patients with mitral valve prolapse. The effective regurgitant orifice increases throughout systole. Regurgitant volume also increases initially but tends to decrease in late systole. These changes can lead to overestimation of the overall degree of regurgitation, but properly timed measurements made by use of the proximal isovelocity surface area method allow an accurate estimation of the overall effective regurgitant orifice.